JP2008307821A - Optical film, manufacturing method and manufacturing apparatus for the same, polarizing plate using optical film, and display unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film in which a cleaning means is elaborated in a serial production of an optical film, thereby vertical vibration phenomenon of an endless belt is made as small as possible, conveying of a stable belt is enabled, and expression of a horizontal step failure of a film surface by passage of time is alleviated, thereby continuous and stable high productivity of an optical film excellent in transparency and planarity is enabled, and consequently requirement of a change into a thin film, broadening, and quality improvement of a protective film for a polarizing plate or the like in recent years can be met, and to provide a manufacturing method and a manufacturing apparatus of the film, a polarizing plate using the optical film, and a display unit. <P>SOLUTION: In the manufacturing method of an optical film by a solution casting film making method, atmospheric pressure plasma or excimer UV is irradiated on a rear surface of an endless belt which carries out rotary drive and/or a roll surface adjacent to the rear surface and/or a roll drum surface adjacent to the rear surface, thereby high energy surface treatment is performed, and deposits such as a plasticizer or the like are eliminated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention can be used for various functional films such as a protective film for a polarizing plate used for a liquid crystal display (LCD), a retardation film, a viewing angle widening film, and an antireflection film used for a plasma display. The present invention relates to a film, a manufacturing method and manufacturing apparatus thereof, a polarizing plate using an optical film, and a display device.

  In recent years, as liquid crystal display devices (LCD) are used in various places, higher productivity (increased production) is also demanded for liquid crystal display elements used in LCDs, that is, polarizing plates. Moreover, LCDs are becoming thinner, and there is a demand for thinner polarizing plates used in LCDs.

  Such a cellulose ester film is generally produced by a solution casting film forming method. In this cellulose ester film production method, first, a cellulose ester is dissolved in a mixed solvent obtained by adding a good solvent for a cellulose ester such as methylene chloride and a poor solvent for a cellulose ester such as methanol, ethanol, butanol or cyclohexane. A cellulose ester resin solution (hereinafter also referred to as a dope) is prepared by adding a plasticizer or an ultraviolet absorber to this, and the dope is transferred to an endless support (for example, endless) having a mirror-finished surface. Cast uniformly from a casting die on a belt (hereinafter also referred to as a support), evaporate the solvent on the support, solidify a dope film (hereinafter also referred to as a web), and then peel it off with a peeling roll This is transferred by a transfer roll and further dried through a drying device or a tenter. And to obtain a cellulose ester film.

  In the method for producing a cellulose ester film by such a solution casting film forming method, with the increase in productivity of the polarizing plate, the productivity (increase in production amount) of the cellulose ester film as a protective film for the polarizing plate is increased. As the film-forming speed increases, the cycle in which the endless belt support for casting becomes dirty has also become shorter.

  In the conventional endless belt casting method, long-term running stability of an endless belt rotating between a pair of winding drums is an important technical problem.

  However, when solution casting film formation is performed over a long period of time, dirt adheres to the endless belt back surface or the roll surface in contact with the endless belt back surface or the winding drum surface in contact with the back surface. When the back of the endless belt comes into contact with the back roll, support roll, or winding drum on the organic matter represented by plasticizers contained therein or machine oil such as lubricating oil that smoothly rotates the endless belt, the back of the belt The stainless steel powder and the inorganic materials such as calcium salt and sodium salt contained in the cellulose ester raw material are adsorbed, and when such dirt accumulates over time, the vertical vibration of the endless belt is expressed, and the optical film Deteriorates the surface smoothness of the film, and causes a lateral failure of the cast film. There is a problem that causes revealed is.

Here, the lateral casting failure of the film means that when the dope is cast from the casting die to the endless belt support, the casting ribbon sways due to vibration of the endless belt support and the width direction of the film The streaks extending in the longitudinal direction of the film are streak-like faults arranged at a pitch of several mm to several tens of mm.
JP 2002-28943 A Patent Document 1 discloses a method for cleaning an endless belt support in the production of a cellulose ester film by a solution casting film forming method. The technique described in Patent Document 1 The surface of the support on the side where the dope (resin solution) is cast is removed.

  As described above, various cleaning techniques for removing dirt on the surface of the endless belt support on the side where the dope (resin solution) is cast have been developed. A technique for cleaning the roll surface in contact with the back surface or the back surface of the endless belt and the surface of the winding drum in contact with the back surface has not been known so far.

  Therefore, conventionally, in order to clean the back surface of the endless belt, the roll surface in contact with the back surface of the endless belt, or the surface of the winding drum in contact with the back surface of the endless belt, which has been contaminated with accumulated organic matter or inorganic material, The surface of the endless belt, the surface of the roll in contact with the back of the endless belt, and the surface of the winding drum in contact with the back of the endless belt are wiped off to remove the deposits.

  However, such a cleaning operation is very inefficient and has a problem that the productivity of the optical film is greatly reduced.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and in the continuous production of an optical film by a solution casting film forming method, on the roll surface and / or the back surface of the endless belt in contact with the back surface of the endless belt. By devising the cleaning means for the surface of the winding drum that comes into contact, the vertical vibration phenomenon of the endless belt is made as small as possible, the belt can be transported stably, and the occurrence of lateral failure on the film surface over time is reduced. It enables continuous and stable high productivity of optical films with excellent transparency and flatness, and in response to the recent demand for thinner, wider and higher quality protective films for polarizing plates. To provide an optical film, a method and apparatus for manufacturing the optical film, a polarizing plate using the optical film, and a display device That.

  In general, atmospheric pressure plasma and excimer UV (excimer UV) are effective for etching organic materials, but are not effective for removing inorganic materials such as calcium, magnesium, and sodium. The back surface of the endless belt or the roll surface in contact with the back surface and / or the removal of dirt on the surface of the winding drum in contact with the back surface has not been expected. However, as a result of extensive research by the present inventors, Alternatively, the surface of the roll in contact with the back surface and / or the surface of the winding drum in contact with the back surface is subjected to high-energy surface treatment by irradiating with atmospheric pressure plasma or excimer UV, and the organic portion of the salt contained in the dirt attached thereto is removed. By disassembling, the salt component and the back surface of the endless belt and / or the Unraveling the fixing of the roll surface and / or the winding drum surface in contact with the back surface, it found that salt component (dirt) is removed, has been led to completion of the present invention.

  In order to achieve the above object, the invention of claim 1 is a method for producing an optical film by a solution casting film forming method, wherein a resin solution (dope) containing a thermoplastic resin and an additive is driven to rotate. The process includes a step of casting on an endless belt (support) to form a cast film (web), evaporating a part of the solvent, and then peeling off from the endless belt. Alternatively, the surface of the roll in contact with the back surface and / or the surface of the winding drum in contact with the back surface is irradiated with atmospheric pressure plasma or excimer UV to perform high energy surface treatment to remove deposits such as plasticizer. .

  The invention according to claim 2 is the method for producing an optical film according to claim 1, wherein the roll in contact with the back surface of the endless belt is a back roll or a support roll.

  The invention of the optical film of claim 3 is characterized by being manufactured by the method of claim 1 or 2.

  The invention of a polarizing plate according to a fourth aspect is characterized in that the optical film according to the third aspect is provided on at least one surface.

  The invention of the display device according to claim 5 is characterized by using the polarizing plate according to claim 4.

  The invention of claim 6 is an apparatus for producing an optical film by a solution casting film forming method, wherein a resin solution (dope) containing a thermoplastic resin and an additive is flowed onto an endless belt (support) that is driven to rotate. An endless belt that includes a casting apparatus that extends and a peeling roll that peels off a part of a solvent contained in a cast film (web) formed on the endless belt and then peels it off from the endless belt. In the vicinity of the back surface and / or the roll surface in contact with the back surface and / or the winding drum surface in contact with the back surface, an atmospheric pressure plasma device or an excimer UV device is provided, and the back surface and / or the back surface of the endless belt that is driven to rotate. The surface of the roll in contact with the surface and / or the surface of the winding drum in contact with the back surface is irradiated with atmospheric pressure plasma or excimer UV to obtain a high energy table. Processing performed is characterized by removing the plasticizer deposits.

  A seventh aspect of the present invention is the optical film manufacturing apparatus according to the sixth aspect, wherein the roll in contact with the back surface of the endless belt is a back roll or a support roll.

  The invention of claim 8 is the optical film manufacturing apparatus according to claim 6 or 7, wherein air curtains are provided on both sides of the atmospheric pressure plasma apparatus or the excimer UV apparatus, and further, exhaust devices are provided on both outer sides thereof. It is characterized by being provided.

  The invention of claim 1 is a method for producing an optical film by a solution casting film forming method, wherein a resin solution (dope) containing a thermoplastic resin and an additive is flowed onto an endless belt (support) that is rotationally driven. Forming a cast film (web), evaporating a part of the solvent, and then peeling off from the endless belt, the back surface of the endless belt to be rotated and / or the roll surface in contact with the back surface and / or Alternatively, the surface of the winding drum in contact with the back surface is irradiated with atmospheric pressure plasma or excimer UV to perform high-energy surface treatment to remove deposits such as plasticizers. Transparency, flatness by minimizing the vertical vibration phenomenon of the film, enabling stable belt transport, and reducing the occurrence of lateral failure on the film surface over time Excellent and enables continuous and stable high productivity of optical films, an effect that eventually recent thinning of the protective films for polarizing plate, it is possible to meet broadening, and demand for higher quality.

  Here, the roll in contact with the back surface of the endless belt is a back roll or a support roll.

  The invention of the optical film of claim 3 is manufactured by the method of claim 1 or 2, and according to the invention of claim 3, the vertical vibration phenomenon of the endless belt is made as small as possible, and a stable belt is produced. Since the film is produced by a method that enables conveyance, the occurrence of lateral failure on the film surface over time is reduced, and the optical film has the effect of being excellent in transparency and flatness.

  Since the invention of the polarizing plate of claim 4 has the optical film excellent in transparency and flatness according to claim 3 on at least one surface, according to the invention of claim 4, the polarizing plate When this is incorporated into a liquid crystal panel, the liquid crystal panel does not cause a decrease in contrast or uneven density, and has an effect of excellent visibility.

  Since the invention of the display device according to claim 5 uses the polarizing plate according to claim 4, according to the invention of claim 5, the liquid crystal panel does not cause a decrease in contrast and unevenness in density, and visibility is improved. There is an effect that it is excellent.

  The invention of claim 6 is an apparatus for producing an optical film by a solution casting film forming method, wherein a resin solution (dope) containing a thermoplastic resin and an additive is flowed onto an endless belt (support) that is driven to rotate. An endless belt that includes a casting apparatus that extends and a peeling roll that peels off a part of a solvent contained in a cast film (web) formed on the endless belt and then peels it off from the endless belt. In the vicinity of the back surface and / or the roll surface in contact with the back surface and / or the winding drum surface in contact with the back surface, an atmospheric pressure plasma device or an excimer UV device is provided, and the back surface and / or the back surface of the endless belt that is driven to rotate. The surface of the roll in contact with the surface and / or the surface of the winding drum in contact with the back surface is irradiated with atmospheric pressure plasma or excimer UV to obtain a high energy table. According to the invention of claim 6, the vertical vibration phenomenon of the endless belt is made as small as possible, the belt can be stably conveyed, and the lateral surface of the film over time can be reduced. By reducing the occurrence of stage failures, it is possible to continuously and stably increase the productivity of optical films excellent in transparency and flatness. There is an effect that it is possible to meet the demand for higher quality.

  The invention of claim 8 is the optical film manufacturing apparatus according to claim 6 or 7, wherein air curtains are provided on both sides of the atmospheric pressure plasma apparatus or the excimer UV apparatus, and further, exhaust devices are provided on both outer sides thereof. According to the invention of claim 8, the atmospheric pressure plasma apparatus or the excimer UV apparatus ensures that the dirt adhered to the back surface of the endless belt, the roll surface in contact with the back surface, or the drum surface in contact with the back surface. By reducing the vertical vibration phenomenon of the endless belt as much as possible, enabling stable belt conveyance, and reducing the occurrence of lateral failure on the film surface over time, transparency and flatness can be achieved. There is an effect that continuous and stable high productivity of an excellent optical film is possible.

  Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  The method for producing an optical film according to the present invention is a method for producing an optical film by a solution casting film forming method, and is an endless belt (support) that rotationally drives a resin solution (dope) containing a thermoplastic resin and an additive. A roll comprising a process of forming a cast film (web) by casting and evaporating a part of the solvent, followed by peeling from the endless belt, and a roll in contact with the back and / or back of the endless belt that is driven to rotate The surface of the winding drum in contact with the front surface and / or the back surface is irradiated with atmospheric pressure plasma or excimer UV (excimer ultraviolet) to perform high energy surface treatment, and the back surface of the endless belt and / or the roll surface in contact with the back surface and / or It removes dirt consisting of organic deposits and inorganic deposits adhering to the surface of the winding drum in contact with the back surface.

  In the above, the roll in contact with the back surface of the endless belt refers to a back roll in contact with the back surface of the dope casting portion of the endless belt and a plurality of support rolls in contact with the back surface of the transport portion of the endless belt.

  Here, the organic deposit is mainly derived from the plasticizer, and generates various organic compounds generated in the process. Furthermore, sublimates, oils and fats, dust, etc. contained in the air are also included. The inorganic deposit is mainly derived from a stainless steel endless belt and produces various inorganic compounds generated in the process. In addition, sublimates and dust contained in the air are also included.

  According to the method of the present invention, the vertical vibration phenomenon of the endless belt is made as small as possible, the stable belt can be conveyed, and the occurrence of lateral failure on the film surface over time can be reduced, thereby improving transparency and flatness. Enables continuous and stable high productivity of excellent optical films.

  An optical film manufacturing apparatus according to the present invention is an optical film manufacturing apparatus based on a solution casting film forming method, and is an endless belt (support) that rotationally drives a resin solution (dope) containing a thermoplastic resin and an additive. The apparatus comprises a casting apparatus for casting on top, and a peeling roll for peeling off from the endless belt after evaporating a part of the solvent contained in the cast film (web) formed on the endless belt. In the vicinity of the back surface of the endless belt and / or the roll surface in contact with the back surface and / or the winding drum surface in contact with the back surface, an atmospheric pressure plasma device or an excimer UV device is provided, and the back surface of the endless belt that is driven to rotate and / or Alternatively, atmospheric pressure plasma or excimer UV (excimer UV) is applied to the roll surface in contact with the back surface and / or the surface of the winding drum in contact with the back surface. By irradiating Shima ultraviolet) subjected to high energy surface treatment is intended to remove the plasticizer deposits.

  According to the optical film manufacturing apparatus of the present invention, the vertical vibration phenomenon of the endless belt is made as small as possible, the belt can be stably conveyed, and the occurrence of lateral failure on the film surface with time is reduced. It enables continuous and stable high productivity of optical films with excellent flatness.

  In the optical film manufacturing apparatus according to the present invention, it is preferable that air curtains are provided on both sides of the atmospheric pressure plasma apparatus or the excimer UV apparatus, and an exhaust apparatus is provided on both outer sides thereof. By such an atmospheric pressure plasma apparatus or excimer UV apparatus, a stain comprising organic and inorganic deposits adhered to the back surface of the endless belt and / or the roll surface in contact with the back surface and / or the surface of the winding drum in contact with the back surface. By removing the endless belt's vertical vibration phenomenon as much as possible, enabling stable belt conveyance, and reducing the occurrence of lateral failure on the film surface over time, transparency and flatness can be removed. It is possible to achieve a continuous and stable high productivity of an optical film having excellent properties.

  In addition, the optical film production method of the present invention includes an excimer on the back surface of the endless belt on which the film is conveyed and / or the roll surface in contact with the back surface and / or the winding drum surface in contact with the back surface during film formation. By irradiating with ultraviolet rays or plasma waves, dirt consisting of organic and inorganic deposits attached to the back surface of the endless belt or the roll surface in contact with the back surface or the winding drum surface in contact with the back surface can be removed. The number of times the film forming operation is interrupted for cleaning is drastically reduced, and the productivity of the optical film can be greatly improved.

  Hereafter, the manufacturing method of the optical film by this invention is described in detail. The optical film can be produced by a solution casting method.

  FIG. 1 is a flow sheet showing a specific example of an apparatus for carrying out the method for producing an optical film of the present invention by a solution casting film forming method. Note that the implementation of the present invention is not limited to the process of the drawings shown below.

  In the figure, the method for producing an optical film by the solution casting film forming method is as follows. First, for example, a cellulose ester resin is dissolved in a mixed solvent of a good solvent and a poor solvent in a dissolution vessel (1), and a plasticizer is added thereto. An additive such as UV absorber is added to prepare a resin solution (dope).

  Next, an endless belt made of, for example, a rotationally driven stainless steel endless belt, in which the dope adjusted in the melting pot is fed to the casting die (3) by a conduit through, for example, a pressurized metering gear pump (2) and transferred infinitely. (6) The dope is cast from the casting die (3) to the upper casting position.

  In order to cast the dope by the casting die (3), there is a doctor blade method in which the film thickness of the cast dope film (web) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. However, a pressure die that can adjust the slit shape of the die portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In addition, as a casting die (3), the pressure die which can adjust the slit shape of a nozzle | cap | die part and is easy to make a film thickness uniform is preferable. The casting die (3) is usually provided with a decompression chamber (4).

  Here, it is preferable that the solid content concentration of the cellulose ester solution (dope) is 20 to 30% by weight. If the solid content concentration of the cellulose ester solution (dope) is less than 20% by weight, sufficient drying cannot be performed on the endless belt (6), and a part of the dope film remains on the endless belt (6) during peeling. This is not preferable because it leads to belt contamination. Also, if the solid content concentration exceeds 30%, the dope viscosity increases, the filter clogging becomes faster in the dope adjustment process, or the pressure increases when cast onto the endless belt (6), and it is not preferable to extrude. Absent.

  One or both of the winding drums (5) and (5) at both the front and rear ends of the rotary drive endless belt (6) are provided with a driving device for applying tension to the endless belt (6), thereby the endless belt. (6) is used in a tensioned state.

  The rotationally driven endless belt (6) includes a pair of front and rear belt end winding drums (5) (5), a back roll (7) for supporting the dope casting portion of the endless belt (6) from the back side of the belt, and an endless It is held by a plurality of support rolls (8) that support the intermediate conveying portion of the belt (6) from the back side of the belt.

  The endless belt (6) is made of, for example, stainless steel (SUS316 or SUS314), the width of the endless belt (6) is 1700 to 2400 mm, the casting width of the cellulose ester solution is 1600 to 2500 mm, and the width of the film after winding Is preferably 1400 to 2500 mm, and the peripheral speed of the endless belt (6) is preferably 40 to 200 m / min.

  The temperature of the endless belt (6) during film formation can be cast at a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, a mixed solvent having a temperature lower than the boiling point of the lowest boiling solvent, Is more preferably in the range of 5 ° C to the boiling point of the solvent-5 ° C. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  The dope cast on the surface of the endless belt (6) as described above also increases the strength (film strength) of the gel film by promoting drying until stripping.

  The dope film (web) (10) formed by the dope cast on the endless belt (6) is heated on the endless belt (6), and the web is removed from the endless belt (6) by the peeling roll (9). Evaporate the solvent until it can be stripped.

  In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back surface of the endless belt (6) by a liquid, a method of transferring heat from the front and back by radiant heat, and the like.

  On the endless belt (6), the amount of residual solvent in the web (10) is preferably dried to 150% by weight or less, and more preferably 30 to 120% by weight. Moreover, as for the web temperature when peeling a web (10) from an endless belt (6), 0-30 degreeC is preferable. Further, immediately after the web (10) is peeled off from the endless belt (6), the temperature rapidly decreases once due to solvent evaporation from the contact surface side of the endless belt (6), and volatile components such as water vapor and solvent vapor in the atmosphere. Is easy to condense, the web temperature during peeling is more preferably 5 to 30 ° C.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M is the weight of the web at an arbitrary time point, and N is the weight when the weight M is dried at 110 ° C. for 3 hours.

  The peeling tension at the time of peeling the web (10) from the endless belt (6) by the peeling roll (9) is usually 50 N / m to 200 N / m, but it is made thinner than before. In the optical film according to the present invention, the amount of residual solvent of the web (10) is large at the time of peeling, and the film tends to shrink in the width direction because the web (10) tends to stretch in the width direction. And since it is easy to wrinkle by folding, it is preferable to peel at a minimum tension that can be peeled off to 170 N / m, and more preferably peel off at a minimum tension of 140 N / m.

  Thus, after drying and solidifying until the web (10) has a peelable film strength on the endless belt (6), the web (10) is peeled by the peeling roll (9), and then from the transport roll (11). The web (10) is stretched in the tenter (14) of the stretching process described later through the front drying device (12).

  In the method for producing an optical film according to the present invention, the back roll (7a) and / or the back surface (6a) in contact with the back surface (6a) and / or the back surface (6a) of the endless belt (6) to be rotationally driven are in contact. The reaction gas (18) is converted into plasma by the atmospheric pressure plasma device (19) and sprayed on the surface of the winding drum (5) (5) in contact with the support roll (8) surface and / or the back surface (6a), Alternatively, excimer UV (excimer ultraviolet) is irradiated by an excimer UV (excimer ultraviolet) apparatus (see FIG. 3 to be described later) to perform high energy surface treatment, and the back surface (6a) and / or the back surface of the endless belt (6). The back roll (7) in contact with the front surface and / or the support roll (8) in contact with the back surface thereof (8) (5) (5) is intended to remove from the consisting dirt organic deposits and inorganic material adhering to the surface.

  In the above, the roll in contact with the endless belt (6) back surface (6a) is the back roll (7) in contact with the back surface (6a) of the dope casting part of the endless belt (6), and the transport unit of the endless belt (6). A plurality of support rolls (8) in contact with the back surface (6a).

  By producing a film by the solution casting film forming method as described above, usually, the back surface (6a) of the endless belt (6) and / or the back roll (7) surface in contact with the back surface and / or the same over time. Organic deposits are deposited on the surface of the support roll (8) in contact with the back surface and / or the surface of the winding drum (5) (5) in contact with the back surface, and the vertical vibration of the endless belt (6) is expressed, thereby smoothing the film. The back surface (6a) of such an endless belt (6) and / or the back roll (7) surface in contact with the back surface and / or the surface of the support roll (8) in contact with the back surface and / or Or the organic deposits on the surface of the winding drum (5) (5) in contact with the back surface are decomposed by irradiation with plasma waves or excimer UV, which is the main feature of the present invention. By removing the inorganic deposits removed from the organic deposits with a suction device, the back surface (6a) of the endless belt (6) and / or the back roll (7) surface in contact with the back surface and / or the same The surface of the support roll (8) in contact with the back surface and / or the surface of the winding drum (5) (5) in contact with the back surface can be kept clean and in contact with the back surface (6a) of the endless belt (6). The back roll (7) surface, the support roll (8) surface in contact with the back surface, and the winding drums (5) and (5) in contact with the back surface are maintained to have a constant adhesion, and the endless belt (6) Excellent transparency and flatness by minimizing the vertical vibration phenomenon as much as possible, enabling stable belt conveyance, and reducing the occurrence of lateral failure on the film surface over time One continuous surface smoothness good high quality optical films and is intended to allow stable high productivity of.

  Next, the atmospheric pressure plasma apparatus will be described in detail.

  The atmospheric pressure plasma apparatus applies a high-frequency voltage between opposing electrodes to discharge, thereby bringing the reactive gas into a plasma state, and the back roll (6a) of the endless belt (6) and / or the back roll in contact with the back surface. (7) A support roll in contact with the front surface and / or the back surface (8) A winding drum (5) in contact with the front surface and / or the back surface (5) By exposing the surface to the reactive gas in the plasma state, an endless belt ( 6) The back surface and / or the back roll (7) in contact with the back surface and / or the support roll (8) in contact with the back surface and / or the winding drum (5) (5) in contact with the back surface. It removes dirt consisting of organic deposits and inorganic deposits.

  In the atmospheric pressure plasma apparatus, a planar system that converts high-frequency power into plasma by applying high-frequency power between electrodes arranged opposite to each other so as to sandwich the substrate to be processed, and a reactive gas that passes between electrodes to which high-frequency voltage is applied are provided. Although there is a downstream system that turns into plasma, the back surface (6a) of the endless belt (6) for film formation of the present invention and / or the back roll (7) in contact with the back surface and / or the support roll in contact with the back surface (8 The latter downstream type is used for the treatment of the surface of the winding drum (5) (5) in contact with the front surface and / or the back surface.

  FIG. 2 is an explanatory diagram for explaining the principle of the atmospheric pressure plasma apparatus.

  In the figure, (a) and (b) are the counter electrodes of the reactor, (h) is the electrode length, (g) is the reactive gas, (w) is the solid dielectric gap, (i) is the air curtain and lamp device cooling Wind, (d) is a gap from the plasma spray slit to the back surface of the endless belt or the roll surface in contact with the back surface of the endless belt, (s) is an endless belt for film formation, and (e) is exhaust.

  As a simple structure of the atmospheric pressure plasma apparatus in FIG. 2, a reaction gas (g) is passed between the counter electrodes (a) and (b) of the reactor to which a high-frequency voltage is applied to convert it into plasma, for example, an endless belt (s ) Is sprayed and supplied to the back surface, and the back surface is processed with high energy.

  In the present invention, the upper limit of the frequency of the high frequency voltage applied between the counter electrodes (a) and (b) of the reactor is preferably 150 MHz or less. In addition, the lower limit value of the frequency of the high-frequency voltage is preferably 200 kHz or more, and more preferably 800 kHz or more.

Further, the lower limit value of the power supplied between the counter electrodes (a) and (b) of the reactor is preferably 1.2 W / cm ² or more, and the upper limit value is preferably 50 W / cm ² or less, and more preferably. Is 20 W / cm ² or less. Note that the voltage application area (/ cm ² ) in the electrode refers to the area in which discharge occurs.

  In addition, the high-frequency voltage applied between the counter electrodes (a) and (b) of the reactor may be an intermittent pulse wave or a continuous sine wave. For this purpose, a continuous sine wave is preferable.

  In the present invention, it is necessary to employ an electrode capable of applying such a high power voltage and maintaining a uniform glow discharge state in the plasma discharge processing apparatus.

  Such an electrode is preferably a metal base material coated with a dielectric. It is preferable to coat a dielectric on at least one side of the opposed application electrode and the ground electrode, and more preferably coat both of the opposed application electrode and the ground electrode with a dielectric. The dielectric is preferably an inorganic substance having a relative dielectric constant of 6 to 45. Examples of such a dielectric include ceramics such as alumina and silicon nitride, silicate glass, borate glass, and the like. Glass lining material and the like.

  The distance between the discharge electrodes is preferably 0.5 mm to 20 mm, more preferably 0.5 mm to 5 mm, and particularly preferably 1 to 3 mm from the viewpoint of performing uniform discharge.

  The plasma blowing slit and the back surface (6a) of the endless belt (6) and / or the back roll (7) in contact with the back surface and / or the support roll (8) in contact with the back surface and / or the back surface are in contact. The gap between the surfaces of the winding drums (5) and (5) is preferably 0.5 to 6 mm, and more preferably 1 to 4 mm. If it is too close, the back surface (6a) of the endless belt (6) and / or the back roll (7) in contact with the back surface and / or the support roll (8) in contact with the back surface and / or the winding drum in contact with the back surface (5) (5) There is a risk of contact and damage to the surface, and if it is separated too much, the back roll and / or the back roll in contact with the back surface (7) and / or the support roll in contact with the back surface ( 8) The effect of removing dirt on the surface of the winding drum (5) (5) in contact with the front surface and / or the back surface is weakened.

  Various reactive gases (g) can be used, but from the viewpoints of environment, exhaust after-treatment, and running cost, a mixture of a small amount of oxygen with nitrogen is preferable. The mixing ratio of oxygen is preferably 0.005 to 0.1% by volume with respect to the volume of the raw material gas.

  The gas flow rate is preferably 20 to 5000 L / min per 1 m of the effective width of plasma irradiation. Furthermore, 40 to 1000 L / min is more preferable.

  If there is a lot of entrained air when the endless belt (6) moves, the plasma gas will flow and the concentration will decrease, and in use during film formation, it will be in a solvent gas atmosphere evaporated from the dope, It is also necessary to suppress their inflow.

  Therefore, it is preferable to install an air curtain or an air knife around the main body, and to install an exhaust duct for sucking exhaust gas and air or solvent gas to enter from the outside of the apparatus.

  Further, in the atmospheric pressure plasma, the back surface (6a) of the endless belt (6) and / or the surface of the back roll (7) in contact with the back surface and / or the surface of the support roll (8) in contact with the back surface by induced current or arc discharge and Since there is concern about damage such as roughening of the surface of the winding drum (5) (5) in contact with the back surface, it is desirable to use an apparatus having a shield mechanism.

  Next, an excimer UV apparatus will be described.

  FIG. 3 is an explanatory diagram for explaining the principle of the excimer UV apparatus.

  In the figure, (u) is an excimer UV lamp, (r) is a reflector, (p) is purge gas, (i) is an air curtain / lamp device cooling air, (s) is an endless belt for film formation, (e) Exhaust.

In the present invention, using the excimer UV lamp (u) shown in FIG. 3, the back surface (6a) of the film-forming endless belt (s) is mainly irradiated with ultraviolet light having a wavelength of 172 nm at a light quantity of 1 to 3,000 mJ / cm ^2. ) And / or the back roll (7) in contact with the back surface and / or the support roll (8) in contact with the back surface and / or the surface of the winding drum (5) (5) in contact with the back surface. . Such ultraviolet rays generate active oxygen and ozone, and the back surface (6a) of the endless belt (s) and / or the back roll (7) surface in contact with the back surface and / or the support roll (8) surface in contact with the back surface. It is possible to decompose organic deposits on the roll surface in contact with the surface of the winding drum (5) (5) in contact with the rear surface.

  Also, the excimer UV lamp (u) and the back surface of the endless belt (s) and / or the back roll (7) in contact with the back surface and / or the support roll (8) in contact with the back surface and / or the back surface If the gap with the surface of the winding drum (5) (5) is too close, the back roll (7) in contact with the back surface and / or the back surface of the endless belt (s) and / or the support roll (8) in contact with the back surface. ) There is a risk of contact or damage to the surface of the winding drum (5) or (5) in contact with the front surface and / or the back surface. If it is separated too much, the high energy of excimer UV is absorbed in oxygen and water, and endless. The back surface of the belt (s) and / or the back roll (7) surface in contact with the back surface and / or the surface of the support roll (8) in contact with the back surface. Beauty / or the smear removal effect of the winding drum (5) (5) in contact with the back surface surface is weakened, preferably 0.5 to 4 mm, more, 1 to 3 mm is more preferable.

  When an excimer UV lamp having a center wavelength of 200 nm or less is selected, ozone is generated due to absorption of oxygen in the air. This ozone has the effect of oxidizing and decomposing organic deposits as much as or shorter than short-wavelength light. When ozone is generated, the decomposition efficiency of organic deposits becomes very high. Therefore, the back surface (6a) of the endless belt (6) and / or the back roll (7) surface in contact with the back surface and / or the support roll (8) surface in contact with the back surface and / or the back surface are exposed to ultraviolet rays. The atmosphere for cleaning the surface of the winding drum (5) (5) is preferably a clean oxygen atmosphere in which dust and the like are not floating, and the back roll (6) and / or the back roll in contact with the back surface ( 7) A support roll in contact with the front surface and / or the back surface (8) A wind drum (5) (5) surface in contact with the front surface and / or the back surface, and an ultraviolet lamp, and an exhaust device is always attached. It is more preferable to supply fresh air.

  Next, in the present invention, a resin solution (dope) for producing an optical film contains a resin such as cellulose ester resin as a main material, and includes a plasticizer, an ultraviolet absorber, fine particles, and a low molecular weight substance. It contains at least one of these substances and a solvent.

  Hereinafter, these will be described.

  In the method for producing an optical film of the present invention, various resins can be used as a film material, and cellulose ester is particularly preferable.

  A cellulose ester is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present invention are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl groups is preferably 2.0 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present invention, the number average molecular weight of the cellulose ester is preferably in the range of 60000 to 300000, since the mechanical strength of the resulting film is strong. Furthermore, 70000-200000 are preferable.

  In the present invention, various additives can be added to the cellulose ester.

  In the method for producing an optical film according to the present invention, an organic solvent having good solubility with respect to the cellulose derivative is referred to as a good solvent, and has a main effect on dissolution. Organic) solvent or main (organic) solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by weight of an alcohol having 1 to 4 carbon atoms. After the dope is cast on the endless belt, the solvent starts to evaporate and the alcohol ratio increases, so that the web (the dope film after the casting of the cellulose derivative dope on the endless belt is referred to as the web). Is used as a gelling solvent that makes the web strong and makes it easy to peel off from the endless belt, or when these ratios are small, dissolve the cellulose derivative of the non-chlorine organic solvent. There is also a role to promote.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving a cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

  The film according to the present invention includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles that impart slipperiness to the film (matting agent), an ultraviolet absorber that imparts an ultraviolet absorbing function, and deterioration of the film. You may contain the antioxidant etc. which prevent.

  The plasticizer used in the present invention is not particularly limited. However, a cellulose derivative or a reactive metal compound capable of hydrolytic polycondensation can be used so as not to cause haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the condensate by hydrogen bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present invention is represented by the following general formula (1).

Formula _{(1) R 1 - (OH} ) n
(However, R ₁ represents an n-valent organic group, and n represents a positive integer of 2 or more.)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Examples of preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose derivative is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Examples of preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, Tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose derivatives.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, and the like can be used, but in the present invention, it is preferable that a phosphate ester plasticizer is not substantially contained.

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by weight, preferably 0.1% by weight, and particularly preferably not added.

  These plasticizers can be used alone or in combination of two or more.

  The amount of the plasticizer used is preferably 1 to 20% by weight. 6 to 16% by weight is further preferable, and 8 to 13% by weight is particularly preferable. If the amount of the plasticizer used is less than 1% by weight relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by weight, the plasticizer bleeds out from the film, and the film Since the physical properties of the material deteriorate, it is not preferable.

  In order to impart slipperiness to the cellulose derivative in the present invention, it is preferable to add fine particles such as a matting agent. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for each film, and the number of particles in 100 μm ² whose major axis length is in the range of 0.05 to 5 μm for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change, and it is important that the fine particles are finally combined with the cellulose ester in the film. It is to control the particle size formed by aggregation.

  Here, if the average particle size of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.5% by weight to the cellulose ester. Preferably, 0.05 to 0.3% by weight, more preferably 0.05 to 0.25% by weight is added. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat the composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used in the present invention is an apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm ² or more. Further, at that time, those having a maximum reaching speed of 100 m / sec or more and those having a heat transfer speed of 100 kcal / hr or more are preferable.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, or a nanomizer manufactured by Nanomizer, and also a Manton Gorin type high-pressure dispersing device such as Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present invention, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a lower alcohol, then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is allowed to flow on an endless belt. A cellulose ester film is obtained which is formed by stretching and drying.

  Here, the content ratio of the lower alcohol is preferably 50 to 100% by weight, more preferably 75 to 100% by weight.

  Examples of lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by weight. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by weight, more preferably 10 to 20% by weight.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  Examples of ultraviolet absorbers that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  As the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  Specific examples of useful UV absorbers in the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-). Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2- Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, 2- (2'-hydroxy) 3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl -3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5 A mixture of-(5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as commercially available products of ultraviolet absorbers, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Specific examples of the benzophenone compounds that are ultraviolet absorbers that can be used in the present invention include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5- Examples thereof include, but are not limited to, sulfobenzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  In this invention, the compounding quantity of these ultraviolet absorbers has the preferable range of 0.01 to 10 weight% with respect to a cellulose ester (cellulose derivative), and also 0.1 to 5 weight% is preferable. If the amount of the ultraviolet absorber used is too small, the ultraviolet absorbing effect may be insufficient. If the amount of the ultraviolet absorber is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  Further, as the ultraviolet absorber that can be used in the optical film of the present invention, the polymer ultraviolet absorber (or ultraviolet absorbing polymer) described in JP-A-6-148430 and JP-A-2002-47357 is preferably used. be able to. In particular, the polymer ultraviolet ray represented by the general formula (1) described in JP-A-6-148430, the general formula (2), or the general formula (3) (7) described in JP-A-2002-47357. Absorbents are preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the film. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0% by weight, more preferably 10 to 1000 ppm by weight with respect to the cellulose derivative.

  In addition, in the apparatus which implements the manufacturing method of the optical film of the present invention shown in FIG. 1 described above, as the film for a liquid crystal display device, the stretching step is performed using clips or the like on both side edges of the web (or film) (10). A tenter method in which the film is fixed and stretched is preferable in order to improve the flatness and dimensional stability of the film.

  The residual solvent amount of the web (film) (10) immediately before entering the tenter (14) in the stretching step is preferably 10 to 35% by weight.

  In the present invention, the stretch ratio of the web in the tenter (14) in the stretching step is 3 to 100%, preferably 5 to 80%, and more preferably 5 to 60%. Moreover, the temperature of the warm air blown from the warm air blowing slit port in the tenter (14) is 100 to 200 ° C, preferably 110 to 190 ° C, and more preferably 115 to 185 ° C.

  It is preferable to provide drying apparatuses (12) and (15) before and after the tenter (14) in the stretching step. In the drying devices (12) and (15), the web (10) is meandered by a plurality of transport rolls (13) and (16) arranged in a staggered manner as viewed from the side, and the web (10) is dried in the meantime. Is. The film transport tension in the drying apparatus (12) (15) is affected by the physical properties of the dope, the amount of residual solvent in the peeling and film transport process, the drying temperature, etc. The film transport tension during drying is 30 to 300 N / width m, more preferably 40 to 270 N / width m.

  The means for drying the web (film) (10) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, a microwave, or the like. It is preferable to dry with hot air from the viewpoint of simplicity. For example, the drying device is dried by the drying air blown from the hot air inlet at the front portion of the bottom of the drying device (12) (15), and the drying device (12) (15). The exhaust air is exhausted from the outlet of the rear portion of the ceiling of the roof, and then dried. The temperature of the drying air is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  For example, a cellulose ester film that has finished the transport drying process is generally processed to form an emboss on the film by an embossing apparatus before the introduction to the winding process.

  Here, the height h (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . Embossing may be formed on both sides of the film. In this case, the height h1 + h2 (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. For example, when the film thickness is 40 μm, the emboss height h 1 + h 2 (μm) is set to 2 to 12 μm. The emboss width is set to 5 to 30 mm.

  The film after drying is wound up by a winding device (17) to obtain the original winding of the optical film. A film having good dimensional stability can be obtained by setting the residual solvent amount of the film to be dried to 0.5% by weight or less, preferably 0.1% by weight or less.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly.

  The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  In the optical film according to the present invention, the width of the film after winding is preferably 1200 to 2500 mm.

  In this invention, the film thickness after drying of a cellulose-ester film has the preferable range of 20-150 micrometers as a finished film from a viewpoint of thickness reduction of a liquid crystal display device. Here, the film thickness after drying refers to a film in which the amount of residual solvent in the film is 0.5% by weight or less.

  Here, when the film thickness of the cellulose ester film after winding is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If the film thickness is too thick, the advantage of thinning the film becomes less than the conventional cellulose ester film. To adjust the film thickness, control the dope concentration, pump feed rate, slit gap of the die of the casting die, the extrusion pressure of the casting die, the speed of the endless belt, etc. Is good. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In the process from immediately after casting through the solution casting film-forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . However, of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be considered.

  In the present invention, the cellulose ester film preferably has a moisture content of 0.1 to 5%, more preferably 0.3 to 4%, and even more preferably 0.5 to 2%.

  In the present invention, the cellulose ester film desirably has a transmittance of 90% or more, more preferably 92% or more, and further preferably 93% or more.

  Moreover, the optical film manufactured by the method of the present invention has a haze of 0.3 to 2.0 when three sheets are stacked. According to the optical film of the present invention, the haze of the film is very high. It is low and has optical characteristics excellent in transparency and flatness.

  Here, the haze of the optical film may be measured using, for example, a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method defined in JIS K6714.

  Moreover, the tensile elastic modulus in the machine direction (MD direction) of the cellulose ester film produced by the method for producing an optical film according to the present invention is 1500 to 3500 MPa, and the tensile elastic modulus in the direction perpendicular to the machine direction (TD direction) is It is preferably 3000 MPa to 4500 MPa, and the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the film is preferably 1.40 to 1.90.

  Here, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the optical film is less than 1.40, the sag of the central portion becomes large in winding a film having a width exceeding 1650 mm, and Since sticking increases, it is not preferable. Further, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction exceeds 1.90, warpage after overheating on the deflecting plate occurs, or the backlight is heated by the heat of the backlight when incorporated in the liquid crystal panel. Since the dimensional change behavior of the polarizing plate on the side and the surface side is greatly different, unevenness occurs at the corner, which is not preferable.

  As a specific method for measuring the tensile modulus of elasticity in the MD direction and TD direction of the film, for example, the method of JIS K7217 can be mentioned.

  That is, using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), a sample was set at a chucking pressure: 0.25 MPa, a distance between marked lines: 100 ± 10 mm, and a pulling speed: 100 ± 10 mm / min. Pull on. As a result, from the obtained tensile stress-strain curve, the elastic modulus calculation start point is 10N, the end point is 30N, and the tangent line drawn between them is extrapolated to calculate the elastic modulus.

  In the optical film of the present invention, the in-plane retardation (Ro) defined by the following formula is 30 to 300 nm under the conditions of a temperature of 23 ° C. and a humidity of 55% RH, and the thickness direction retardation (Rt) is a temperature of 23 ° C. It is preferable that it is 70-400 nm on the conditions of humidity 55% RH.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the film. The refractive index in the thickness direction (refractive index measured at a wavelength of 590 nm), d represents the thickness (nm) of the film.

  The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, using KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), the wavelength can be obtained at 590 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH.

  According to the optical film of the present invention, since the vertical vibration phenomenon of the endless belt is made as small as possible and the belt can be conveyed stably, the occurrence of lateral failure on the film surface with time is reduced. The optical film is excellent in transparency and flatness.

  The optical film produced by the method of the present invention is preferably used for a liquid crystal display member, specifically a protective film for a polarizing plate. In particular, an optical film produced by the method of the present invention is preferably used in a protective film for a polarizing plate that has strict requirements for moisture permeability and dimensional stability.

  Furthermore, since the display device of the present invention uses the polarizing plate described above, the liquid crystal panel does not cause a decrease in contrast and uneven density, and has excellent visibility.

  By the way, the polarizing film is a film that has been conventionally stretched by treating a film that can be stretched and oriented, such as a polyvinyl alcohol film, with a dichroic dye such as iodine. Since the polarizing film itself does not have sufficient strength and durability, a polarizing plate is generally obtained by adhering a cellulose ester film having no anisotropy as a protective film to both surfaces thereof.

  The polarizing plate may be prepared by laminating the optical film produced by the method of the present invention as a retardation film, and the optical film produced by the method of the present invention is a retardation film and a protective film. Alternatively, it may be produced by directly bonding to a polarizing film. The method of bonding is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution. Furthermore, a long polarizing plate can be obtained by laminating a long polarizing film stretched in the longitudinal direction and treated with a dichroic dye and a long retardation film produced by the method of the present invention. . A polarizing plate is a sticking type in which a peelable sheet is laminated on one or both sides thereof via a pressure sensitive adhesive layer (for example, an acrylic pressure sensitive adhesive layer). Or the like can be easily attached).

  The polarizing plate thus obtained can be used for various display devices. In particular, a liquid crystal display device using a VA mode liquid crystal molecule in which liquid crystal molecules are substantially vertically aligned when no voltage is applied, or a TN mode liquid crystal cell in which liquid crystal molecules are substantially horizontal and twisted when no voltage is applied. Is preferred.

  By the way, a polarizing plate can be produced by a general method. For example, there is a method in which an optical film or a cellulose ester film is alkali saponified, and a polyvinyl alcohol film is dipped in an iodine solution and stretched on both sides of a polarizing film prepared by using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment of immersing the cellulose ester film in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesiveness.

  The optical film produced by the method of the present invention includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optical anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer, Various functional layers such as an adhesive layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, or atmospheric pressure plasma treatment.

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and a liquid crystal display device is obtained using this.

  By using the protective film for a polarizing plate comprising the optical film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning.

  Since the polarizing plate of the present invention has an optical film excellent in transparency and flatness on at least one surface, when the polarizing plate of the present invention is incorporated in a liquid crystal panel, the contrast of the liquid crystal panel is reduced or the unevenness of the light and shade It is excellent in visibility.

  In the present invention, the liquid crystal display device comprises two sheets comprising a liquid crystal cell in which rod-like liquid crystal molecules are sandwiched between a pair of glass substrates, a polarizing film disposed so as to sandwich the liquid crystal cell, and transparent protective layers disposed on both sides thereof. It has a polarizing plate.

  By using the protective film for polarizing plates made of the optical film produced by the method of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as in a thin film. Furthermore, a liquid crystal display device using this polarizing plate or retardation film can maintain stable display performance over a long period of time.

  The optical film produced by the method of the present invention can also be used as a base material for an antireflection film or an optical compensation film.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1
(Preparation of dope)
The following materials were put into a closed container, heated, stirred and completely dissolved and filtered to prepare a dope. Silicon dioxide fine particles (Aerosil R972V) were added after being dispersed in ethanol.

(Dope composition)
Cellulose triacetate (acetyl substitution degree 2.88) 100 parts by weight Triphenyl phosphate 8 parts by weight Biphenyl diphenyl phosphate (liquid plasticizer) 4 parts by weight 5-chloro-2- (3,5-di-sec-butyl-2- Hydroxyphenyl) -2H-benzotriazole (liquid UV absorber) 1 part by weight Methylene chloride 418 parts by weight Ethanol 23 parts by weight Aerosil R972V 0.1 part by weight Calcium (Ca), magnesium remaining as impurities in the cellulose triacetate ( The analysis method of Mg) and the measured values are as follows.

(Analysis method)
After ashing 500 mg of vinegar cotton in an electric furnace (800 ° C., 1 hour), it was dissolved in nitric acid and finished to 50 ml, and all elements were qualitatively detected by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer). Quantification was performed on the elements.

(measured value)
Ca: 64 ppm
Mg: 12ppm
(Production of cellulose triacetate film)
Using the above dope, a cellulose triacetate film having a thickness of 40 μm was produced as follows.

  As shown in FIG. 1, the filtered dope was uniformly cast from a coat hanger die (3) on an endless belt (6) made of SUS316 and having a temperature of 20 ° C. at a dope temperature of 35 ° C.

  After the web (10) is peeled from the endless belt (6), the web (10) is dried while being conveyed in a roll at 90 ° C. in the front dryer (12), and the residual solvent amount in the tenter (14). When it was 10%, the film was stretched 1.06 times in the width direction in an atmosphere of 100 ° C. Thereafter, the width holding is released, and the stretched film (web) (10) is rolled and conveyed to a drying zone (rear drying device) (15) at 125 ° C. to finish drying. Winding by (17), a cellulose triacetate film having a film thickness of 40 μm was produced.

  In this embodiment, the back surface (6a) of the rotationally driven endless belt (6), the back roll (7) surface in contact with the back surface, the support roll (8) surface in contact with the back surface, and the front and back windings in contact with the back surface. The surface of each of the rotating drums (5) and (5) is irradiated with the following atmospheric pressure plasma by the atmospheric pressure plasma apparatus shown in FIG. 2 to perform high energy surface treatment, and the back surface (6a) of the endless belt (6). ), A back roll (7) surface in contact with the back surface, a support roll (8) surface in contact with the back surface, a winding drum (5) in contact with the back surface (5), and an organic deposit and an inorganic deposit adhered to the surface. Dirt was removed.

(Atmospheric pressure plasma treatment)
The length h of the counter electrode of the reactor is 30 mm, the solid dielectric gap w is 1 mm, the power supplied to the high-frequency oscillator is 9 kW, the back surface (6a) of the endless belt (6) from the plasma injection slit, and the back roll in contact with the back surface (7) Support roll in contact with the front surface and the back surface (8) 0.1 m / min under the condition that the gap d to the surface of the winding drum (5) and (5) in contact with the back surface is 3 mm While carrying the endless belt (6) at a speed of, atmospheric pressure plasma irradiation treatment was performed. The composition of the mixed gas (reactive gas) used for the atmospheric pressure plasma treatment is described below. The atmospheric pressure was 1.0 atm.

Nitrogen 99.98% by volume
Oxygen 0.02% by volume
Mixed gas flow rate 2m ³ / min
The film formation of the cellulose triacetate film was continuously performed for 2 weeks under the above conditions, and the film thickness deviation of the cellulose triacetate film after the start of film formation, 1 week later, and 2 weeks later was measured with a surface roughness meter, and the film surface The level of cast lateral failure was judged. Further, the back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, and the support roll (8) surface in contact with the back surface after one week and two weeks after the start of film formation The surfaces of the winding drums (5) and (5) in contact with the back surface were visually observed to evaluate the respective stains.

  The film thickness deviation was measured at 50 mm square with a surface roughness measuring machine (SURFTEST SV-3100) manufactured by Mitutoyo Corporation. The back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, the support roll (8) surface in contact with the back surface, and the winding drum (5) (5) surface in contact with the back surface are dirty. When it comes, it is confirmed that the film thickness deviation observed by the surface roughness measuring machine is increased, and the back surface (6a) of the endless belt (6) is in contact with the back surface from the surface roughness measuring machine. The back roll (7) surface, the support roll (8) surface in contact with the back surface, and the winding drum (5) in contact with the back surface (5) (5) The degree of progress of the casting horizontal stage failure due to dirt on the surface was evaluated.

  Also, the lateral failure of the cast film means that when the dope is cast from the casting die (3) to the endless belt (6), the casting ribbon is shaken by the vibration of the endless belt (6), etc. The stripes extending in the width direction are arranged at a pitch of several mm to several tens of mm in the longitudinal direction. When the horizontal cast failure of the film is conspicuous, when the film is mounted on a liquid crystal display panel as a part of the polarizing plate, it is scattered at the streaks and appears uneven or streaky, which is very conspicuous The film becomes unusable as a product.

  There is the following relationship between the film thickness deviation of the film and the level of cast lateral failure. Also, the back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, the support roll (8) surface in contact with the back surface, and the winding drum (5) (5) surface in contact with the back surface Was also evaluated visually.

A: The film thickness deviation is 0.15 μm or less. No streak is visually observed, and the film has no casting horizontal stage failure. O: Film thickness deviation is 0.20 μm or less. While moving the film to the point light source,
When you hold it over, you can see faint streaks, but the film has almost no cast lateral failure, and there is no problem in use as a product. Δ: Film thickness deviation is 0.25 μm or less. When the film is held over a point light source, streaks are observed, and there is a slight level failure in the cast, but it is at a level that can be used as a product. ×: Thickness deviation of 0.30 μm or more. Table 1 below shows the results obtained. At first glance, the streaks were found, the film had a cast lateral failure, and could not be used as a product.

Example 2
Although it carries out similarly to the case of the said Example 1, the point which is different from the case of the said Example 1 differs in the atmospheric pressure plasma process, the back roll (7) surface which touches the back surface (6a) of an endless belt (6), and It is in the point performed with respect to the support roll (8) surface which touches the back surface.

  Then, film formation was carried out continuously for 2 weeks under the same conditions as in Example 1 above, and the film thickness deviation of the cellulose triacetate film after the start of film formation and after 1 week and 2 weeks was measured with a surface roughness meter. In addition, the level of the cast lateral failure on the film surface was judged. Further, the surface of the back roll (7) in contact with the back surface (6a) of the endless belt (6) and the surface of the support roll (8) in contact with the back surface after 1 week and 2 weeks after the start of film formation were visually observed. And evaluated each stain.

  The obtained results are shown in Table 1 below.

Example 3
Although it carries out similarly to the case of the said Example 1, the point which is different from the case of the said Example 1 exists in the point which performed the atmospheric pressure plasma process with respect to the back surface (6a) of the endless belt (6).

  Then, film formation was carried out continuously for 2 weeks under the same conditions as in Example 1 above, and the film thickness deviation of the cellulose triacetate film after the start of film formation and after 1 week and 2 weeks was measured with a surface roughness meter. In addition, the level of the cast lateral failure on the film surface was judged. Furthermore, the back surface (6a) of the endless belt (6) at the start of film formation and after one week and two weeks later was visually observed to evaluate each stain.

  The obtained results are shown in Table 1 below.

Example 4
Although it implements similarly to the case of the said Example 1, the point which is different from the case of the said Example 1 differs in the atmospheric pressure plasma process in the winding drum (5) (5) which contact | connects the back surface (6a) of an endless belt (6). ) It is a point made on the surface.

  Then, film formation was carried out continuously for 2 weeks under the same conditions as in Example 1 above, and the film thickness deviation of the cellulose triacetate film after the start of film formation and after 1 week and 2 weeks was measured with a surface roughness meter. In addition, the level of the cast lateral failure on the film surface was judged. Further, the front and rear winding drums (5) and (5) in contact with the back surface (6a) of the endless belt (6) at the start of film formation and after one week and two weeks later, were visually observed, and each dirt was observed. Evaluated.

  The obtained results are shown in Table 1 below.

Comparative Example 1
Although it carries out similarly to the case of the said Example 1, the point different from the case of the said Example 1 exists in the point which formed the film for 2 weeks, without performing atmospheric pressure plasma processing.

  Then, the film thickness deviation of the cellulose triacetate film after the start of film formation, one week later, and two weeks later was measured with a surface roughness meter, and the level of the casting lateral failure on the film surface was judged. Further, the back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, and the support roll (8) surface in contact with the back surface after one week and two weeks after the start of film formation The surfaces of the winding drums (5) and (5) in contact with the back surface were visually observed to evaluate the respective stains.

  The obtained results are shown in Table 1 below.

Examples 5-8
Although it carries out similarly to the case of the said Examples 1-4, the point which is different from the case of the said Examples 1-4 uses an excimer UV apparatus shown in FIG. 3 instead of the atmospheric pressure plasma apparatus shown in FIG. The excimer UV treatment is applied. That is, the following excimer UV treatment is performed on the back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, the support roll (8) surface in contact with the back surface, and the winding drum in contact with the back surface ( 5) (5) It was applied to the surface, and the dirt consisting of organic deposits and inorganic deposits adhered to each surface was removed.

(Excimer UV treatment)
In an apparatus containing four Xe ₂ wavelength 172 nm excimer UV lamps having a width of 1600 mm, an irradiated glass length of about 300 mm, and an irradiance of 40 mW / cm ² , the back surface of the endless belt (6) (6a ), A back roll (7) surface in contact with the same back surface, a support roll (8) surface in contact with the same back surface, and a winding drum (5) (5) surface in contact with the back surface, with each gap being 3 mm under irradiation conditions, Excimer UV irradiation treatment was performed while conveying the endless belt (6) at a speed of 0.1 m / min.

  Film formation was performed continuously for 2 weeks under the above conditions, and the film thickness deviation of the cellulose triacetate film after the start of film formation, 1 week later, and 2 weeks later was measured with a surface roughness meter. The level of failure was judged. Further, the back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, and the support roll (8) surface in contact with the back surface after one week and two weeks after the start of film formation The surfaces of the winding drums (5) and (5) in contact with the back surface were visually observed to evaluate the respective stains.

The obtained results are shown in Table 1 below.

  As is clear from the results of Table 1 above, according to Examples 1 to 8 of the present invention, the back surface (6a) of the endless belt (6), the back roll (7) surface in contact with the back surface, and the support in contact with the back surface. Organic deposits deposited on the surface of the roll (8) and the winding drum (5) (5) in contact with the back surface are decomposed by irradiation with atmospheric pressure plasma waves or excimer UV waves, which is the main feature of the present invention. By removing the inorganic deposits removed from the organic deposits with a suction device, the back surface (6a) of the endless belt (6), the back roll (7) in contact with the back surface, and the support in contact with the back surface The surface of the roll (8) and the winding drum (5) (5) in contact with the back surface can be kept clean, and a high-quality cellulose triacetate film with good surface smoothness can be produced stably over a long period of time. I was able to.

Example 9
Next, using the cellulose triacetate film prepared in Examples 1 to 8 and Comparative Example 1 as a protective film for polarizing plate, the polarizing plate of the present invention was prepared and evaluated according to the method described below.

1. Production of Polarizing Film A long polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a long polarizing film.

2. Next, according to the following processes 1-5, the polarizing film and the cellulose triacetate film were bonded together and the polarizing plate was produced.

  Step 1: The long cellulose triacetate films prepared in Examples 1 to 8 and Comparative Example 1 were immersed in a 2 mol / L sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried. A protective film (manufactured by polyethylene terephthalate) that can be peeled off in advance was attached to the surface provided with the antireflection film for protection.

  Similarly, a commercially available long cellulose ester film (trade name KC4UY, manufactured by Konica Minolta Opto Co., Ltd.) was immersed in a 2 mol / L sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried.

  Process 2: The above-mentioned long polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly removed, and it was sandwiched between the cellulose triacetate film subjected to alkali treatment in Step 1 and the cellulose ester film, and laminated.

Process 4: It bonded together by the speed of about 2 m / min with the pressure of 20-30 N / cm < ² > with the two rotating rollers. At this time, care was taken to prevent bubbles from entering.

  Step 5: The sample prepared in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to prepare a polarizing plate.

(Evaluation of polarizing plate)
The cellulose of Examples 1 to 8 of the present invention in which the polarizing plate on the outermost surface of a commercially available liquid crystal display panel (NEC color liquid crystal display, MultiSync, LCD1525J, model name LA-1529HM) was carefully peeled off and the polarization direction was adjusted here. A polarizing plate using a triacetate film and a polarizing plate using the cellulose triacetate film of Comparative Example 1 were attached to each other. And about each liquid crystal display panel, the nonuniformity which looks whitish when it sees from the front and diagonally by several evaluators was observed. The obtained results are shown in Table 1 above.

Evaluation criteria for unevenness ○ None of the evaluators can see unevenness at all △ Some evaluators may see slight unevenness, but the level that can be used as a product × Many evaluators showed faint but unevenness. As is clear from the results, the liquid crystal display panel to which the polarizing plates using the cellulose triacetate films of Examples 1 to 8 of the present invention were attached had no defects due to foreign matters, and the cellulose triacetate film of Comparative Example 1 was used. It was confirmed that the liquid crystal display panel on which the polarizing plate was attached had no unevenness in reflected light and was excellent in display performance.

It is a flow sheet which shows the specific example of the apparatus which enforces the manufacturing method of the optical film of this invention. It is explanatory drawing for demonstrating the principle of the atmospheric pressure plasma apparatus used in the manufacturing method of the optical film of this invention. It is explanatory drawing for demonstrating the principle of the excimer UV apparatus used in the manufacturing method of the optical film of this invention.

Explanation of symbols

1: melting pot 2: pump 3: casting die 4: decompression chamber 5, 5: front and rear winding drum 6: rotationally driven endless belt 6a: back surface of endless belt 7: back roll 8: support roll 9: peeling roll 10: Web (film)
12: Front roll transport drying device 14: Tenter 15: Rear roll transport drying device 17: Winder 18: Reactor gas 19: Atmospheric pressure plasma irradiation device a: Reactor counter electrode b: Reactor counter electrode h: Electrode length g: Reaction gas w: Solid dielectric gap i: Air curtain / lamp device cooling air d: Gap from plasma spray slit to back of endless belt s: Endless belt for film formation e: Exhaust u: Excimer UV of excimer UV device Lamp r: reflector p: purge gas q: quartz glass

Claims (8)

  A method for producing an optical film by a solution casting film-forming method, wherein a resin solution (dope) containing a thermoplastic resin and an additive is cast on an endless belt (support) that is rotationally driven to cast a film ( Web), a part of the solvent is evaporated and then peeled off from the endless belt, and the back surface of the endless belt to be driven and / or the roll surface in contact with the back surface and / or the winding drum in contact with the back surface A method for producing an optical film, wherein the surface is subjected to high-energy surface treatment by irradiating atmospheric pressure plasma or excimer UV to remove deposits such as a plasticizer.   The method for producing an optical film according to claim 1, wherein the roll in contact with the back surface of the endless belt is a back roll or a support roll.   An optical film manufactured by the method according to claim 1.   A polarizing plate comprising the optical film according to claim 3 on at least one surface.   A display device comprising the polarizing plate according to claim 4.   An apparatus for producing an optical film by a solution casting method, a casting apparatus for casting a resin solution (dope) containing a thermoplastic resin and an additive on an endless belt (support) that is driven to rotate; A peeling roll that peels off the endless belt after evaporating a part of the solvent contained in the cast film (web) formed on the endless belt, and is in contact with the back and / or back of the endless belt that is driven to rotate; In close proximity to the roll surface and / or the surface of the winding drum in contact with the back surface, an endless belt back surface and / or the back surface and / or the back surface which is provided with an atmospheric pressure plasma device or an excimer UV device and is driven to rotate. High-energy surface treatment is performed by irradiating the surface of the winding drum in contact with atmospheric pressure plasma or excimer UV, and plasticizers, etc. And removing the clothes, the manufacturing apparatus of an optical film.   The apparatus for producing an optical film according to claim 6, wherein the roll in contact with the back surface of the endless belt is a back roll or a support roll.   8. The apparatus for producing an optical film according to claim 6, wherein an air curtain is provided on both sides of the atmospheric pressure plasma apparatus or the excimer UV apparatus, and an exhaust device is provided on both outer sides thereof.

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